[ https://issues.apache.org/jira/browse/HADOOP-4049?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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George Porter updated HADOOP-4049:
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Affects Version/s: 0.18.0
0.18.1
Release Note:
Added an IPC Instrumentation API and supporting classes. These APIs also support path-state,
or state that is passed along the RPC datapath.
Status: Patch Available (was: Open)
This patch incorporates feedback from the online discussion, resulting in:
* 6 instrumentation points (4 for normal calls, 2 for exceptional conditions)
* Support for those points setting and querying path-state kept along the path
* wrapping the IPC path state into an object with its own type
* More cleanly separating the RPC layer from the IPC layer. The IPC call() method has
been extended to include per-call state.
* Test cases
> Cross-system causal tracing within Hadoop
> -----------------------------------------
>
> Key: HADOOP-4049
> URL: https://issues.apache.org/jira/browse/HADOOP-4049
> Project: Hadoop Core
> Issue Type: New Feature
> Components: dfs, ipc, mapred
> Affects Versions: 0.18.1, 0.18.0
> Reporter: George Porter
> Attachments: HADOOP-4049.2-ipc.patch, HADOOP-4049.patch, multiblockread.png,
multiblockwrite.png
>
>
> Much of Hadoop's behavior is client-driven, with clients responsible for contacting individual
datanodes to read and write data, as well as dividing up work for map and reduce tasks. In
a large deployment with many concurrent users, identifying the effects of individual clients
on the infrastructure is a challenge. The use of data pipelining in HDFS and Map/Reduce make
it hard to follow the effects of a given client request through the system.
> This proposal is to instrument the HDFS, IPC, and Map/Reduce layers of Hadoop with X-Trace.
X-Trace is an open-source framework for capturing causality of events in a distributed system.
It can correlate operations making up a single user request, even if those operations span
multiple machines. As an example, you could use X-Trace to follow an HDFS write operation
as it is pipelined through intermediate nodes. Additionally, you could trace a single Map/Reduce
job and see how it is decomposed into lower-layer HDFS operations.
> Matei Zaharia and Andy Konwinski initially integrated X-Trace with a local copy of the
0.14 release, and I've brought that code up to release 0.17. Performing the integration involves
modifying the IPC protocol, inter-datanode protocol, and some data structures in the map/reduce
layer to include 20-byte long tracing metadata. With release 0.18, the generated traces could
be collected with Chukwa.
> I've attached some example traces of HDFS and IPC layers from the 0.17 patch to this
JIRA issue.
> More information about X-Trace is available from http://www.x-trace.net/ as well as in
a paper that appeared at NSDI 2007, available online at http://www.usenix.org/events/nsdi07/tech/fonseca.html
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